PROJECT SUMMARY STEEP Project 4, Detection and Bioaccumulation, will develop, validate and deploy novel passive samplers for the detection of poly- and perfluoroalkyl substances (PFASs) in water and porewater, thereby directly addressing the Superfund Research Program (SRP)?s mandate to develop new tools for the detection of hazardous compounds. At contaminated sites, as the extent of a PFAS plume is investigated, active water sampling is labor- and time-intensive, prone to sampling/contamination artifacts and does not necessarily reflect typical conditions. The benefits of field-validated passive sampling approaches include (i) ease of handling; (ii) ease of shipping to/from sampling sites; (iii) ease of analysis without time-consuming extractions; (iv) reduced potential for contamination; and (v) lower detection limits that will be needed as regulatory agencies adjust their references doses. Project 4 focuses on three innovative research components, consisting of the development and field validation of three novel detection tools: (i) developing the PFAS porewater fiber for measuring PFAS concentrations in porewater to deduce partitioning and bioavailability, and comparing results to those from controlled bioaccumulation tests for PFAS accumulation in bivalves, in collaboration with the U.S. EPA; (ii) field validating a PFAS sampling tube for reporting time weighted average (TWA) concentrations in water, and (iii) validating a passive polyethylene PFAS precursor sampler for reporting precursor concentrations. Preliminary results indicate that the PFAS sampling tube functions as a diffusive sampler, implying that the uptake of PFASs depends on their molecular diffusivity, not on the water flow outside of the sampler tube. Once PFAS diffusivities are characterized by Project 4, water concentrations of PFASs can easily be derived. The partitioning of non-ionic PFAS precursors into the polyethylene sampler follows predictions based on hexadecane-water partitioning, and that polyethylene samplers accumulate PFASs in surface waters. Project 4 is well-integrated within STEEP. Sites for field validation and application will be located on Cape Cod, MA, the primary site of the Community Engagement Core activities, and will engage residents and stakeholders to address concerns about long-range PFAS transport and characterize the extent of impacted ponds, creeks and estuaries. Project 4 will work closely with Project 1 (transport and fate) through common field deployments of passive samplers in ponds near Joint Base Cape Cod, where groundwater is contaminated by aqueous film forming foams, and work with Project 3 (rodent model) on tissue analysis and characterizing basic properties for PFASs. Lastly, Project 4 will work with the Research Translation Core and U.S. EPA to translate results and applications of passive samplers for PFASs to state and federal agencies, and with the Training Core on lectures (detection, sampling), laboratory activities (detection, QA/QC) and field trips (deployment, sampling).